Abstract
This study examined the role of ferrite (tempered martensite) characteristics on the austenite mechanical stability and the mechanical properties of medium Mn steel. It was found that the morphology of ferrite in the annealed microstructure has a significant impact on the austenite mechanical stability and mechanical properties of medium Mn steel. The large massive ferrite grains distributed minimal strain during tensile loading, resulting in significant interphase strain incompatibility and consequently low total elongation and austenite mechanical stability of the experimental steel. Inserting a short-duration high-temperature annealing into the traditional intercritical annealing (IA) process can reduce the proportion of blocky ferrite grains by promoting the nucleation of austenite within the defect-free martensite block in the hot-rolled microstructure of the experimental steel. By adjusting the duration of high-temperature annealing, it is possible to simultaneously optimize the ferrite morphology and intrinsic mechanical stability of austenite, drastically enhancing the mechanical properties of medium Mn steel. In this study, the total elongation of the experimental steel increased from 25.1% to 46.3%, and the product of strength and elongation (PSE) increased from 25.75 GPa·% to 52.78 GPa·%. Ferrite regulation provides a new strategy for medium Mn steel to overcome strength-ductility trade-off through simple processing.
Published Version
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